[PATCH] cgroup: fix psi_show() crash on 32bit ino archs

[PATCH] cgroup: fix psi_show() crash on 32bit ino archs

[Qian Cai]

Similar to the commit d7495343228f ("cgroup: fix incorrect
WARN_ON_ONCE() in cgroup_setup_root()"), cgroup_id(root_cgrp) does not
equal to 1 on 32bit ino archs which triggers all sorts of issues with
psi_show() on s390x. For example,

 BUG: KASAN: slab-out-of-bounds in collect_percpu_times+0x2d0/
 Read of size 4 at addr 000000001e0ce000 by task read_all/3667
 collect_percpu_times+0x2d0/0x798
 psi_show+0x7c/0x2a8
 seq_read+0x2ac/0x830
 vfs_read+0x92/0x150
 ksys_read+0xe2/0x188
 system_call+0xd8/0x2b4

Fix it by using cgroup_ino().

Fixes: 743210386c03 ("cgroup: use cgrp->kn->id as the cgroup ID")
Signed-off-by: Qian Cai <cai@lca.pw>
---
 kernel/cgroup/cgroup.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 75f687301bbf..cd5f41289f7d 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -3542,21 +3542,21 @@ static int cpu_stat_show(struct seq_file *seq, void *v)
 static int cgroup_io_pressure_show(struct seq_file *seq, void *v)
 {
 	struct cgroup *cgrp = seq_css(seq)->cgroup;
-	struct psi_group *psi = cgroup_id(cgrp) == 1 ? &psi_system : &cgrp->psi;
+	struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi;
 
 	return psi_show(seq, psi, PSI_IO);
 }
 static int cgroup_memory_pressure_show(struct seq_file *seq, void *v)
 {
 	struct cgroup *cgrp = seq_css(seq)->cgroup;
-	struct psi_group *psi = cgroup_id(cgrp) == 1 ? &psi_system : &cgrp->psi;
+	struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi;
 
 	return psi_show(seq, psi, PSI_MEM);
 }
 static int cgroup_cpu_pressure_show(struct seq_file *seq, void *v)
 {
 	struct cgroup *cgrp = seq_css(seq)->cgroup;
-	struct psi_group *psi = cgroup_id(cgrp) == 1 ? &psi_system : &cgrp->psi;
+	struct psi_group *psi = cgroup_ino(cgrp) == 1 ? &psi_system : &cgrp->psi;
 
 	return psi_show(seq, psi, PSI_CPU);
 }
-- 
2.21.0 (Apple Git-122.2)

Re: [PATCH] cgroup: fix psi_show() crash on 32bit ino archs

[Johannes Weiner]

On Sun, Feb 23, 2020 at 10:00:07PM -0500, Qian Cai wrote:
> Similar to the commit d7495343228f ("cgroup: fix incorrect
> WARN_ON_ONCE() in cgroup_setup_root()"), cgroup_id(root_cgrp) does not
> equal to 1 on 32bit ino archs which triggers all sorts of issues with
> psi_show() on s390x. For example,
> 
>  BUG: KASAN: slab-out-of-bounds in collect_percpu_times+0x2d0/
>  Read of size 4 at addr 000000001e0ce000 by task read_all/3667
>  collect_percpu_times+0x2d0/0x798
>  psi_show+0x7c/0x2a8
>  seq_read+0x2ac/0x830
>  vfs_read+0x92/0x150
>  ksys_read+0xe2/0x188
>  system_call+0xd8/0x2b4
> 
> Fix it by using cgroup_ino().
> 
> Fixes: 743210386c03 ("cgroup: use cgrp->kn->id as the cgroup ID")
> Signed-off-by: Qian Cai <cai@lca.pw>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

Re: [PATCH] cgroup: fix psi_show() crash on 32bit ino archs

[Qian Cai]

On Mon, 2020-02-24 at 11:29 -0500, Johannes Weiner wrote:
> On Sun, Feb 23, 2020 at 10:00:07PM -0500, Qian Cai wrote:
> > Similar to the commit d7495343228f ("cgroup: fix incorrect
> > WARN_ON_ONCE() in cgroup_setup_root()"), cgroup_id(root_cgrp) does not
> > equal to 1 on 32bit ino archs which triggers all sorts of issues with
> > psi_show() on s390x. For example,
> > 
> >  BUG: KASAN: slab-out-of-bounds in collect_percpu_times+0x2d0/
> >  Read of size 4 at addr 000000001e0ce000 by task read_all/3667
> >  collect_percpu_times+0x2d0/0x798
> >  psi_show+0x7c/0x2a8
> >  seq_read+0x2ac/0x830
> >  vfs_read+0x92/0x150
> >  ksys_read+0xe2/0x188
> >  system_call+0xd8/0x2b4
> > 
> > Fix it by using cgroup_ino().
> > 
> > Fixes: 743210386c03 ("cgroup: use cgrp->kn->id as the cgroup ID")
> > Signed-off-by: Qian Cai <cai@lca.pw>
> 
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>

Tejun, can you take a look at this when you had a chance?

Re: [PATCH] cgroup: fix psi_show() crash on 32bit ino archs

[Tejun Heo]

On Sun, Feb 23, 2020 at 10:00:07PM -0500, Qian Cai wrote:
> Similar to the commit d7495343228f ("cgroup: fix incorrect
> WARN_ON_ONCE() in cgroup_setup_root()"), cgroup_id(root_cgrp) does not
> equal to 1 on 32bit ino archs which triggers all sorts of issues with
> psi_show() on s390x. For example,
> 
>  BUG: KASAN: slab-out-of-bounds in collect_percpu_times+0x2d0/
>  Read of size 4 at addr 000000001e0ce000 by task read_all/3667
>  collect_percpu_times+0x2d0/0x798
>  psi_show+0x7c/0x2a8
>  seq_read+0x2ac/0x830
>  vfs_read+0x92/0x150
>  ksys_read+0xe2/0x188
>  system_call+0xd8/0x2b4
> 
> Fix it by using cgroup_ino().
> 
> Fixes: 743210386c03 ("cgroup: use cgrp->kn->id as the cgroup ID")
> Signed-off-by: Qian Cai <cai@lca.pw>

Applied to cgroup/for-5.6-fixes.

Thanks.

-- 
tejun